2D - scale sprite to one fifth of screen

So I have a square sprite (width == height) and I want to scale it so that both width and height are exactly one fifth of the screen. How should I proceed?

So…

spriteHeight = Mathf.RoundToInt(Screen.height * 0.20f);
spriteWidth = Mathf.RoundToInt(Screen.width * 0.20f);

Apply to sprite.